1. Field of the Invention
The invention relates to a roller guide assembly, especially for a billet, bar or wire rolling-mill roll stand train.
2. Description of the Prior Art
Such roller guide assemblies serve to guide the materail to be rolled in a train roll stand with the right orientation into the pass of two grooved rolls of the roll stand and also to prevent any twisting of the material about its longitudinal axis as it runs through the roll pass, such twisting being likely to occur if the material has an elongated cross section, as for example the cross section of a diamond or an oval cross section, and if it runs upright between the two grooved rolls into a flat or circular pass thereof in order to be plastically deformed in such a way that its major cross section axis is shortened. In order to securely hold the material the roller guide assemblies include two guide rollers having an outline matching the shape of the material cross section and the axis-to-axis distance of which is so set in accordance with the cross section of the material to be rolled that the same runs between the two guide rollers in a completely play-free manner, which contact the material with a predetermined pressure. This relative adjustment of the guide rollers is generally undertaken outside the respective roll stand in a workshop using mechanical or optical measuring instruments, whereupon the roller guide assembly is fitted to the roll stand, a careful adjustment of the roller guide assembly relative to the respective roll pass being performed in order to ensure that the axes of the cross section of the material to be rolled are aligned with the axes of the pass cross section.
Generally the roller guide assemblies consist of a housing holding an entry guide member which guides the material to be rolled between the two guide rollers and two arms supporting the guide rollers and pivotally mounted on the housing for rocking about two axes parallel to the axes of rotation of the guide rollers, each rocking axis being located substantially in the center between the two ends of the respective supporting arms, on which the guide roller thereof is mounted for rotation and respectively a setting screw is disposed by which the supporting arm may be pivoted in relation to the housing on setting the axis-to-axis distance between the two guide rollers. The housing is adapted to be secured to a roll stand to be fitted with a roller guide assembly in a position which may be accurately set with respect to the roll pass of the roll stand.
Given meticulous adjustment, roller guide assemblies of this type make possible a very high rolling speed of up to 100 meter/sec, the guide rollers being supported on ball, roller or taper roller bearings, which are lubricated with an air-oil mixture. However, problems arise inasfar as although the guide rollers or their axis-to-axis distance are very accurately set at the start of the rolling process to a predetermined cross section of the material to be rolled, in a rolling-mill with a train of roll stands, this cross section will change owing to wear thereof, the wear of the grooved rolls and that of the guide rollers taking place at different rates. At high speeds of rolling these wear rates are also very high so that the rolling operation will become unsatisfactory after only a comparatively short time, because the rolling-mill roll stand train will have lost its correct adjustment. For this reason a further increase in the speed of rolling is regarded as being unpromising.
It is known to spring-load the guide roller supporting arms of such roller guide assemblies so that even in the case of a reduction in the cross section of the material passing therethrough one may be certain of an accurate guiding action and in the case of an increase in cross section the guide rollers and their bearings will not be over loaded (see German utility model 7,415,378 and German patent application 2,646,006). However, this does not make it possible to maintain the original adjustment of a roll stand train.